<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>后盾人</title>
  </head>
  <body></body>
  <script>
    // let a = { url: "houdunren" };
    // let b = { name: "后盾人" };
    // // Object.prototype.web = "hdcms.com";
    // // console.log("web" in a);
    // Object.setPrototypeOf(a, b);
    // // console.log("name" in a);
    // // console.log(a.hasOwnProperty("name"));
    // for (const key in a) {
    //   if (a.hasOwnProperty(key)) {
    //     console.log(a[key]);
    //   }
    // }
    class User {
      name = 'llq';
      sing() {
        console.log('User.sing');
      }
    }

    class Admin extends User {
      constructor() {
        super();
      }
      sing() {
        console.log('Admin.sing');
      }
    }
    const admin = new Admin();
    console.dir(admin);
    admin.sing();
  </script>
</html>
